I struggle with this a lot. As many above have responded, there are pros and cons to everything in the world, but everything has to be used in its proper time.
I can't argue that Smart phones have definitely made improvements to the quality of life - as many have pointed out they're indispensable in many business cases, and enable us to take care of certain things faster and more efficiently. As others have pointed out - where would we be without Waze? Messaging apps? In many ways my phone has replaced many of the things I used to need to carry - keys, credit cards, a camera, all rolled into one. Remember all of those life moments where you wish you had a camera - now you have one in your back pocket! Forgot your wallet at home on a trip to the store - pay by phone.
At the same time, I think that the smartphone has contributed to increased levels of anxiety and exacerbated ADHD in people. It's also exacerbated the availability expectations employers have of employees. All the years I did technical support, I dreaded turning on my Blackberry/Smartphone after shabbos to find urgent e-mails, or worse, hitting refresh waiting for e-mails to arrive. Your boss expecting you to answer e-mails off hours and on weekends. (Yes my bosses are aware I am shomer shabbos, but expect a response sat. night or sunday).
Think about it does to people with ADHD - the constant buzz that pulls you away from whatever task you are doing. The FOMO of missing an important text message, and constantly checking. It all takes a toll on our mental well being.
So I guess what I am saying is it's a mixed bag.
For a lighter side of this argument - I wrote this in 2017, I hope that some of you enjoy it -
https://medium.com/@yonahwolf/1994-vs-2009-vs-2017-94ce7a7b6e53